# Statistical Skills AQA AS Level Geography (unit 2)

The AQA specification requires you to know

• measures of central tendency – mean, mode,

median

• measures of dispersion – interquartile range and

standard deviation

• Spearman’s rank correlation test

Here is a simple explanation of them all.

- Created by: Annie
- Created on: 28-05-12 10:40

First 172 words of the document:

Geography Skills Paper

Interquartile Range

Step 1: Put the numbers in order

1,2,5,6,7,9,12,15,18,19,27

Step 2: Find the median (How to find a median)

1,2,5,6,7,9,12,15,18,19,27

Step 3: Find Q1 and Q3

Q1 can be thought of as a median in the lower half of the data, and Q3 can be thought of as

a median for the upper half of data.

(1,2,5,6,7), 9, ( 12,15,18,19,27). Q1=5 and Q3=18.

Step 4:Subtract Q1 from Q3 to find the interquartile range.

185=13.

Standard deviation

Column 2 here stands for the deviant (rainfall (x) the average rainfall)

Column 3 here stands for the deviant squared (rainfal (x) the average rainfall) SQUARED.

Standard deviation describes how spread out the data is. If the data all lies close to the mean,

then the standard deviation will be small, while if the data is spread out over a large range of

values, will be large.

Mode: result that occurs most frequently.

Mean: Sum of all the results/ the number of results.

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